Metal–semiconductor
heterostructures have been arousing
enduring interest on account of the pivotal roles of metal nanocrystals
(NCs) as interfacial Schottky junction-induced charge flow mediators
and surface plasmon resonance-triggered photosensitizers. Tungsten
oxide (WO3) stands out among fruitful semiconductors by
virtue of favorable energy-level alignment and light absorption capability,
but slow charge transfer rate, especially the sluggish hole transport
kinetics and short life span of charge carriers, retards its widespread
photocatalytic applications. In this work, an efficient and unidirectional
charge-transfer channel was constructed in the in situ-formed gold
nanoparticle (Au NP)-decorated WO3 [Au/WO3 nanorods
(NRs)] heterostructures which were constructed by a facile, green,
easily accessible, and efficacious layer-by-layer (LbL) self-assembly
strategy at ambient conditions, wherein the in situ generation of
Au NPs and the morphology transformation of WO3 NRs to
a mesoporous ensemble occur simultaneously. Moreover, the deposition
amount of Au NCs on the WO3 matrix can be finely tuned
by the assembly cycle. Intriguingly, the unique integration mode of
Au NPs with the WO3 matrix at the nanoscale level endowed
by the LbL self-assembly benefits the high-efficiency extraction,
separation, and migration of energetic charge carriers photoinduced
over WO3 NRs. It was found that self-assembled Au/WO3 heterostructures demonstrate highly efficient and versatile
photoredox performances toward mineralization of organic pollutants
and photoreduction of heavy metal ions under both simulated solar
and visible light irradiation, substantially outperforming the single
WO3 counterpart. This is predominantly ascribed to the
crucial role of Au NPs as electron traps rather than the plasmonic
photosensitizers to accelerate the interfacial electron transfer,
thereby considerably enhancing the separation and prolonging the lifetime
of photoinduced electron–hole pairs. In addition, predominant
active species in the photoredox catalysis were unambiguously determined,
and the photocatalytic mechanism was clearly elucidated. Our work
would open up new frontiers to rationally design a large variety of
metal–semiconductor heterostructures for promising solar energy
conversion.